The objective of this project is to develop an imaging system to allow visualization of small cancerous tumors and guide biopsy of the prostate. In the course of the Phase l R43CA96153 project and subsequent development sponsored by private funds, we defined the parameters for a commercially viable laser optoacoustic imaging system (LOIS-P) for detection of prostate cancer and developed the first laboratory prototype suitable for phantom testing and experiments in dogs. Our initial test results encouraged the submission of a Phase ll proposal for development of a commercial prototype of LOIS-P and its extensive evaluation in the canine model of prostate cancer. This system will operate in real time and will be capable of imaging the prostate gland and guiding a biopsy procedure. Current methods of medical imaging are only marginally successful in differentiating between cancerous and normal prostate tissue. As a result, biopsies are typically performed with random sampling of tissue throughout the prostate (yielding about a 30% false negative rate). Optoacoustic imaging utilizes the highest known physical or chemical contrast of cancerous tissues relative to normal or benign tissue based on absorption of blood in the tumor microvessels and provides images with excellent resolution of 0.5 mm typical of ultra wide-band ultrasonic imaging. Based on imaging results from 25 breast cancer patients, LOIS has already demonstrated clinical feasibility in diagnostic imaging of malignant tumors in the breast. We will utilize experience gained in the continuing Phase-ll project for development of a clinical breast imaging system to develop a more advanced system for guiding biopsy of the prostate. The focus of the 1st year project will be on development and fabrication of (1) a transrectal probe incorporating a fiberoptic light delivery system with an array of 128 ultrawide-band ultrasonic transducers and charge preamplifiers, and (2) a beam forming and data acquisition and processing circuit board with firmware capable of dual imaging with conventional ultrasound and optoacoustics. The 2nd year will be dedicated to extensive evaluation of transrectal LOIS-P in a canine model of prostate cancer and iterative optimization of the developing system in preparation for clinical testing in humans. Successful accomplishment of the proposed project will make the optoacoustic imaging system available for clinical evaluation as a feature of a transrectal ultrasound system. [unreadable] [unreadable] [unreadable]